This invention relates to packaged potable liquid such as bottled water, and, particularly, relates to a potable liquid packaging which does not impart an off-taste to the potable liquid.
Water packaged in plastic containers is a large segment of the beverage market. Historically, water packaged in plastic containers develops an off-taste after a short period of storage. This off-taste is often described as a xe2x80x9cplasticxe2x80x9d off-taste and is most pronounced in water packaged in polyolefin containers, but is also noted in containers made of other plastics, such as PET, especially if the container is closed with a polyolefin closure.
It is known to those skilled in the art that the plastic off-taste can be correlated with the presence of long-chain aldehydes, particularly the aldehydes such as octanal, nonanal, decanal, and decenal. These aldehydes are detectable in water at the part per billion (ppb) level. Although the plastic off-taste is noticeable in all waters packaged in plastic containers, it is particularly noticeable if the water has been treated with ozone prior to packaging.
The origin of the plastic off-taste is commonly thought to arise from thermal degradation of the polyolefins during processing; consequently, antioxidants are frequently added to the polyolefins to inhibit these degradation reactions. This approach achieves some reduction in the amount of plastic off-taste developed during storage of water in these containers; however, a plastic off-taste is frequently still noticeable.
Prior art inventions to address this problem, such as PCT patent application WO 96/04833, involve the addition of agents that can complex with aldehydes. Unfortunately, because of the low concentration of these aldehydes and their significant solubility in water, this approach only removes a small portion of the aldehydes.
Consequently, there remains a need for plastic packaging that does not impart a plastic off-taste to water. It is therefore an object of the present invention to prevent formation of plastic off-taste in water packaged in plastic containers.
It has now been discovered that the formation of aldehydes during thermal processing of polyolefins, and particularly on exposure to ozonated water, is not due to the thermal degradation of the polyolefins themselves, but rather is due to the degradation of the ethylenically unsaturated slip agents and lubricants used. These lubricants are typically unsaturated fatty acid amides. As lubricants, the fatty acid amides are used to improve mold flow and mold release for polyolefins. Slip agents improve the torque removal properties of the closure. In other words, slip agents make it easier to remove a closure which has been tightly threaded onto a container.
A particularly popular lubricant is erucamide. Erucamide is also used almost universally as a slip agent in polyolefin closures. In this role, the erucamide functions to reduce the coefficient of friction between the closure liner (or closure shell) and the container finish. Without such a slip agent, removal torques for such closures would be unacceptably high. Erucamide is widely used as a slip agent and lubricant because of its low cost and useful properties. Erucamide is a C-22 fatty acid amide that possesses a double bond at the C-13 position. Ozone, in particular, is extremely effective at selectively cleaving this double bond, creating the C-9 aldehyde nonanal.
Therefore, the present invention is directed toward polyolefin compositions for closure shells, closure liners, and containers that avoid the formation of aldehydes such as nonanal. This invention encompasses polyolefin compositions that are substantially free of ethylenically unsaturated additives. This invention also encompasses the use of these polyolefin compositions for the packaging of water, especially ozonated water.
More particularly, this invention solves the above described problem in the prior art by providing potable liquid packaging which is substantially free of an ethylenically unsaturated compound, and packaged potable liquids including such packaging. The packaging of this invention can include a container having an opening and a removable closure for sealing the opening, wherein the container or the closure, or both, comprise a shell including a plastic matrix which is substantially free of an ethylenically unsaturated compound. Desirably, the container shell or closure shell, or both, comprise a substantially fully ethylenically saturated slip agent dispersed in the respective plastic matrix.
Alternatively, the removable closure can include a liner comprising a plastic matrix and an organic slip agent dispersed in the plastic matrix of the liner, wherein the slip agent is substantially fully ethylenically saturated and the liner is substantially free of an ethylenically unsaturated compound. Because any slip agent in the closure shell, container shell or liner is ethylenically saturated, ozone does not react with the slip agent and produce aldehydes which cause plastic off-taste. The slip agent allows for easy removal of the closure even when tightly threaded onto the associated container.
Desirably, the organic slip agent has an iodine value of less than 10, more desirably less than 5, more desirably less than 1, and still more desirably has an iodine value of 0. The iodine value is a number expressing the percentage, in grams per 100 grams, of iodine absorbed by a substance and is a measure of the proportion of unsaturated linkages present in an organic compound.
Furthermore, the closure shell, the container shell, and liner, are at least 99.98% free of an ethylenically unsaturated compound and more desirably is at least 99.99% free of ethylenically unsaturated compound. In other words, the container shell, the closure shell, or the liner can include trace amounts of unsaturated compound but not enough to produce sufficient quantities of aldehydes when exposed to ozone to create a plastic off-taste detectable by human taste. Most desirably, the container shell, the closure shell, and/or the liner is 100% free of ethylenically saturated compound.
The packaged potable liquid of this invention comprises a potable liquid, such as water, disposed within the container of the packaging described above. Water packaged according to this invention is desirably ozonated.
Accordingly, an object of this invention is to provide potable liquid such as water packaged in plastic containers, but having little or no plastic off-taste.
Other objects, features, and advantages will be apparent from the following detailed description of embodiments, drawings, and claims.